CN111033357A

CN111033357A - Head-up display

Info

Publication number: CN111033357A
Application number: CN201880053990.1A
Authority: CN
Inventors: W·冯施皮格尔
Original assignee: Continental Automotive GmbH
Current assignee: Continental Automotive Technologies GmbH
Priority date: 2017-08-22
Filing date: 2018-08-17
Publication date: 2020-04-17
Also published as: WO2019038201A2; WO2019038201A3; DE102017214592A1; KR102468923B1; US20200264431A1; EP3673317A2; KR20200026301A; US11531198B2

Abstract

The invention relates to a head-up display having a display element (1), a projection system (2), a diffuser plate (3) and a mirror element (4, 41). In such a head-up display, confusion due to disturbance light often occurs. Therefore, a head-up display that produces less confusion by incident disturbance light is desirable. It is proposed that the diffuser plate (3) has a focusing element (31) on its side facing the projection system (2) and a shadow mask (32) on its side facing away from the projection system (2).

Description

Head-up display

Technical Field

The present invention relates to a head-up display with a projection/projection system.

Background

Patent document US 2016/0335959 a1 shows a head-up display having a display element, a projection system, a diffuser plate (/ diffuser plate) and a mirror element. In the known head-up display, it is disadvantageous that disturbing light incident on the diffuser plate from directions external to the projection system is reflected by the surface of the diffuser plate in directions in which the disturbing light can pass through the optical system to the eyes of the observer and thereby become confused at the observer.

A head-up display that is less confusing to incoming disturbing light would be desirable.

Disclosure of Invention

According to the invention, in a head-up display with an intermediate image generation unit consisting of a display element and a projection system, a diffuser plate and a mirror element, it is proposed that the diffuser plate has a focusing element on its side facing the projection system and a shading mask on its side facing away from the projection system. This has the advantage that the mask blocks the interference light, so that the interference light no longer reaches the projection system or the direction of the intermediate image plane and no interference reflections and the like occur here. The focusing element focuses the light from the projection system on the opening of the mask so that almost all the light from the projection system also reaches the mirror element and thus the direction of the observer. Due to the focusing element, the light is directed in a reasonable angular range for the viewer. Also disturbing reflections in the diffusing element by total internal reflection, also known as TIR, are effectively reduced by the assembly according to the invention.

The display element is a self-emitting display element (for example an OLED display based on organic light-emitting diodes), a light-transmitting display element (for example a liquid crystal-based LCD display), or a reflective display element (for example a DMD display based on digital micromirrors). An image of the display element is projected and magnified by the projection system. In certain cases, a reduced projection may also be appropriate. The diffuser plate is arranged in an intermediate image plane of the projection system. The image on the diffuser plate is converted into a virtual image by a virtualization system and superimposed with the environment by means of mirror elements. In many cases, a windshield of the vehicle or a so-called combiner arranged between the windshield and the observer is used as a mirror element. Instead of a diffuser plate, other, non-disc-shaped diffuser elements may also be used, as appropriate. For example, a combination of a turning mirror and a concave mirror is used as a virtualization system.

Preferably, the light blocking mask is made of a material that absorbs light. This has the advantage that disturbing light incident in the direction of the projection system is absorbed by the mask. The disturbing light arriving through the opening of the mask and reflected by the focusing element reaches for the most part on the rear part of the mask, where it is absorbed. Only a small, inconsequential part of the scatter returns through the opening of the mask a second time or is not reflected by the focusing element onto the mask and thus reaches the eye of the observer as disturbing light. In this way, disturbing light, such as sunlight, incident into the head-up display is effectively reduced.

According to the invention, the shadow mask is made of a reflective material and the diffuser plate is arranged inclined with respect to the optical axis of the virtualization system. This has the advantage that the incident sunlight is reflected, but due to the inclined arrangement of the diffuser plate, it does not reach the mirror elements and thus does not have a disturbing effect on the observer. If the optical axis of the virtualized system cannot be determined without any problem, provision is made for: the diffuser plate is tilted in the light path such that light incident from the outside via the virtualization system cannot be reflected again to the outside by the diffuser plate or only a very small portion is reflected to the outside by the diffuser plate, and thus does not have a disturbing effect on the viewer. The shadow mask can advantageously also be designed to be reflective on one side and absorptive on the other side.

Stipulating: the focusing elements are constituted by a field of microlenses, also called a microlens array. This has the advantage that: such a microlens array can be manufactured cost-effectively.

According to the invention, provision is made for: the microlenses of the microlens array are arranged obliquely. The microlenses are tilted according to the distance from the optical axis, so that the emitted light beam entering through the opening of the mask has the best possible matching to the virtualization system. This has the advantage that the viewer sees all areas of the diffuser plate uniformly in the virtual image. This tilting is achieved in a simple manner by arranging the individual microlenses in a manner which is offset to different degrees with respect to the openings in the mask. Thus, light incidence occurring at a distance other than the corresponding optical axis of each microlens has an effect corresponding to the tilt. The pure offset simplifies the manufacture of the microlens array with respect to the tilt.

Advantageously, the diffuser plate has a further surface structure above the shadow mask. This has the advantage that beam shaping is thereby achieved without additional components having to be arranged in the beam path. This saves installation space. The surface structure is formed, for example, by a plurality of lens surfaces arranged next to one another, wherein the number can also be sufficiently small, in the limit case, the only lens surface being provided as a surface structure. Further alternatively, the mask itself may have a surface structure. The surface structure can be designed, for example, as a fresnel lens as a diffuser or as a structure which achieves other desired effects. If such a surface structure is arranged below the mask, this has the advantage that, depending on the function of the mask, little back reflection occurs when disturbing light is incident from above.

According to the invention, the further surface structure is a surface structure which performs the function of a field lens. This has the advantage that the field lens required anyway in head-up displays is integrated into the diffuser plate. For this purpose, the surface structure is designed, for example, as a fresnel lens structure. If the microlens assembly is provided as a surface structure, it is combined with a microlens array to perform an in-situ lens function. By suitably selecting the distance of the lenses of the two micro-lens assemblies, a suitable field lens effect is achieved.

Advantageously, the openings of the mask occupy less than 5% of the area of the mask. This has the advantage that, in the ideal case, more than 95% of the disturbance light is already eliminated when it is incident on the mask for the first time. As a result of the small opening area, the light focused by the focusing element leaves the opening of the mask at an opening angle of about 30 °, which is very suitable for use in head-up displays.

Instead of the display element and the projection system, a variant of the head-up display according to the invention has a further intermediate image generation unit, preferably a phase modulator or a laser scanning system. In such an intermediate image generation unit, disturbing reflections can also be significantly reduced by the diffuser plate according to the invention.

According to the invention, the focusing elements are arranged irregularly on the surface of the diffuser plate. This has the advantage, inter alia, of suppressing moire patterns.

A better suppression of the moire pattern is achieved when the focusing element itself has an irregular shape.

Alternatively or additionally, it is provided that the focusing elements have a common structural dimension. I.e. no structures significantly larger or significantly smaller than the average occur. This prevents large-area, visible changes upon irradiation.

According to the invention, the focusing element has a circular shape and/or an elongated shape and/or an irregular shape. In particular, the result of the mixing of these shapes is a particularly good suppression of the moire pattern.

The optical unit for a head-up display according to the present invention has a display element, a projection system, and the above-described diffusion plate. The optical unit is suitable for forming a head-up display according to the invention in combination with a mirror element and has the advantages described above for the head-up display according to the invention. The optical unit is often an economical unit which, when installed in a vehicle, forms a head-up display together with a mirror element, in particular a windscreen, located in the vehicle.

In the method according to the invention for producing a head-up display, a focusing element is first produced on a first side of a carrier of a diffuser plate. This is achieved, for example, by means of a correspondingly designed casting model, by means of which the diffusing element is produced. A mask is applied on a second side thereof opposite the first side. The mask can, for example, block light and is here not only absorbent on both sides, but also in the direction of the diffuser plate and is reflective on the side facing away from the diffuser plate. Instead of a mask that blocks light, a further mask, for example a photoresist, can also be provided here. Subsequently, the first side is irradiated with a radiation beam having defined geometrical properties, such as intensity and duration, which are suitable for producing openings in the mask. In this case, if necessary, in combination with an etching medium or other suitable measures. Subsequently, the diffuser plate is combined with a projection system and a display element which are capable of generating a beam of rays of said defined geometrical properties. This has the advantage of ensuring that the diffuser plate together with the mask is optimally matched to the projection system. Further alternatively, the diffuser plate and the projection system are first combined and subsequently illuminated through the projection system combined with the diffuser plate. In this way it is also ensured that the diffuser plate and the projection system are optimally matched to one another. Here, a process consisting of laying, irradiation, acid etching and bonding can also be used. Also, pulse-scan based or other suitable methods are reasonably used herein.

In a method according to an aspect of the invention, also referred to as the "Lift-Off method" (Lift-Off-Verfahren), a photoresist is applied on the back side of the lens array. The photoresist is irradiated through the lens array and remains at the irradiated locations, i.e., where openings should later be present. Subsequently, a light-tight mask is applied. Subsequently, the remaining photoresist is dissolved, thereby also removing the mask located on the photoresist. Thereby, the opening of the mask is made.

In the production method according to the invention, provision is made for an adhesive to be applied to the second side of the diffuser plate before the combination, for the microlens assembly to be applied to the adhesive, for the microlens assembly to be subsequently aligned relative to the focusing element, and for the adhesive to be subsequently cured. This is an effective solution for manufacturing a diffuser plate with micro-lens assemblies. Purely adhesive, clamping or non-curable adhesives can also be used here as appropriate.

Drawings

These and other variants and advantages of the invention will be apparent from the following description of embodiments and from the drawings. Wherein:

figure 1 shows a head-up display in a schematic view,

the diffuser plate is shown in figure 2 of the drawings,

figure 3 shows a variant of the diffusion lens,

figure 4 shows a variant of the head-up display,

figure 5 shows an exemplary microlens array,

figure 6 shows an exemplary microlens array,

figure 7 shows a method of manufacture in which,

figure 8 shows a flow chart of a manufacturing method,

figure 9 shows a partial enlargement of figure 2,

fig. 10 shows a variant of the head-up display.

Detailed Description

Fig. 1 shows a head-up display according to the invention, having a display element 1, a projection system 2, a diffuser plate 3 and a mirror element 4. The mirror element 4 is in this case designed as a windshield 41 of a motor vehicle. The display element 1 is illuminated by a light source 11. Light from the light source 11 is reflected on the display element 1 in the direction of the projection system 2. The projection system projects the image of the display element onto the diffuser plate 3 in enlargement or (if designed accordingly) in reduction. Where the image is reflected by the turning mirror 44 onto the concave mirror 45, which again magnifies the image and transforms it into a virtual image. Light from the concave mirror 45 is reflected on the mirror element 4, the windshield 41, and into the eyes 42 of the observer. At this time, the image is superimposed with an image of the environment that is viewable through the windshield 41, and appears as a virtual image VB above the hood of the vehicle or even in front of the vehicle in the direction of travel in front of the windshield.

It can be seen that the diffuser plate 3 has a focusing element 31 on its lower side in the figure. The focusing element 31 faces the projection system 2. On the side of the diffuser plate 3 facing away from the projection system 2, a shadow mask 32 is present. The shadow mask 32 has an opening 321 through which light coming from the projection system 2 and focused by the focusing element 31 passes and reaches the direction of the turning mirror 44.

In the subsequent figures, the same reference numerals as described above are used for identical or identically acting elements. Individual elements need not be re-described unless needed for further understanding.

Fig. 2 shows the diffuser plate 3 according to the invention in an enlarged view. Light from the lens 21 of the projection system 2 is visible, which is focused by the focusing element 31 on the opening 321 of the shadow mask 32. The corresponding light beams are shown by means of solid lines, the propagation direction being indicated by arrows. Furthermore, it can be seen that disturbance light LS, which is indicated by a dashed line, falls from the top right onto the diffuser plate 3. The disturbing light is in particular sunlight, which, in unfavorable conditions, impinges on the head-up display and typically reaches the diffuser plate 3 via a virtualization system formed here by the turning mirror 44 and the concave mirror 45. In the left part of the figure, it can be seen that disturbance light LS1 incident through one of the openings 321 of the light shielding mask 32 is reflected on the boundary surface of one of the focusing elements 31 and enters from below onto the light shielding mask 32. For this purpose, reference is also made to fig. 9, in which the dashed area 9 is shown enlarged. The mask 32 is absorptive on its side facing the focusing element 31, so that here the disturbing light LS1 reaching this side from below is absorbed. On the right side, disturbance light LS2 is shown, which is reflected on the upper side of the light-shielding mask 32. According to a variant of the invention, the shadow mask 32 is also made absorptive on its upper side, so that the disturbance light LS2 is also absorbed by the shadow mask 32 and does not cause confusion. The focusing element 31 is a microlens 311 arranged in a microlens array. In the left part of the figure, the individual microlenses 312, 313, 314 are arranged obliquely with respect to the other microlenses. That is, its axis of symmetry is not perpendicular to the plane of the diffuser plate 3, but is inclined to a different extent depending on the distance from the center. This serves to distribute the light directed to the edge of the diffuser plate 3 as optimally as possible. Here, the microlenses 312 and 314 arranged obliquely are shown only by way of example, and the inclination angles are not necessarily shown to scale, but the principle should be explained at this time. For example, the opening 321 may also be configured as a transparent region of the mask 32, which is formed as a photosensitive film.

The light used emerges from the projection system 2, after passing through the focusing element 31 or other components of the diffuser plate 3 that may be present, through the opening 321 of the shadow mask 32, which serves as an aperture mask. If the emission direction should be further controlled, the microlenses 311 and 314 are implemented to be tilted in an appropriate manner and to match the positions of the openings. When the side facing the sunlight, in this embodiment the upper side, is made absorbent, the disturbance light LS, LS1, LS2 is blocked when the disturbance light is incident on the shadow mask 32. When the side of the mask 32 facing the sunlight is embodied reflective, for example, disturbing light (for example disturbing light LS2 is shown) is reflected. This is typically combined with a tilting of the diffuser plate 3, see fig. 4. In this way, the disturbance light LS2 is guided from the optical path into the light trap. When the side facing the sun is reflective (upper side in the figure) the disturbing light is usually better suppressed than when it is designed to be absorptive on the side facing the sun, since good absorbers are not common. However, measures to avoid reflections into the eyes 42 of the driver are then required, such as tilting or similar effects. On the side facing the projection device, the lower side in the figure, an absorptive layer is arranged (as shown). Otherwise, there is a risk that light travels uncontrolled in the diffuser plate 3 and thus may cause a reduction in contrast.

Fig. 3 shows a further variant of the diffuser plate 3 according to the invention. In this variant, a further surface structure 33 is arranged in the figure above the shadow mask 32. The surface structure is likewise composed of a plurality of microlenses 331 arranged side by side, which are configured such that they, in combination with the lower focusing element 31, perform the field lens function. Here, the microlenses 331 above the mask 32 and the microlenses 311 below the mask 32 in the central region of the diffusion plate 3 are not shifted/not deviated relative to each other, so that light is hardly deflected in the central region. The farther the microlenses 331, 311 are from the central region, the more the microlenses 331, 311 deviate from each other, so that light passes through the diffusion plate 3 in a manner more strongly inclined with respect to the optical axis in the outer region farther from the optical axis. Thereby, the field lens effect is realized by the different separation distances of the microlenses 331 and 311. The light extending from the diffuser plate 3 in the direction of the mirror element 4 has an opening angle and an orientation preset by the design of the surface structure 33. Here, an interference light beam LS2 can be seen, which is incident on the shadow mask 32 via the microlens 331 and is absorbed there. The mask 32 shown in fig. 3 is designed to be absorptive on both sides. The second surface structure 33 is used for further shaping of the light used. One advantage resides in the possibility of incorporating a field lens function with a uniform lens array. An embodiment with a reflective side facing the sun is an option that can be reasonably applied under suitable boundary conditions. In the region 10, as an alternative, the surface structure 34 of the diffuser plate 3 arranged above the mask 32 is shown exemplarily and schematically on the left. Instead of the surface structure 33, this surface structure 34 is provided, which is applied as a separate layer. On the right side of the region 10, a surface structure 35 of the diffuser plate 3 arranged below the mask 32 is schematically and schematically shown. The surface structure 35 has a microstructure that produces the fresnel effect. For example, a bevel disposed below the opening of the mask 32 can be seen. The arrangement of the surface structures 35 below the mask 32 has the advantage that, owing to the function of the mask 32, little back reflection occurs when disturbing light is incident from above.

Fig. 4 shows a variant of the head-up display according to the invention. The optical elements are arranged substantially the same as described in connection with fig. 1. The difference is that the diffuser plate 3 is arranged obliquely with respect to the optical axis of the light coming from the virtualization system, in this embodiment, the turning mirror 44 and the concave mirror 45. The angle of inclination is not necessarily shown to scale here, but is shown exaggerated to illustrate the principle. It can be seen that the disturbance light LS from the sun 40, which is shown in dashed lines, after passing through the windshield 41 extends at the same angle as the light from the concave mirror 45, which is shown in solid lines, but in the opposite direction. Subsequently, the disturbance light LS reaches the head-up display. The disturbance light is reflected by the concave mirror 45 and the turning mirror 44, and is incident on the light-shielding mask 32 of the diffusion plate 3. The shadow mask 32 shown here has a reflective surface on its side facing away from the focusing element 31, so that the disturbing light LS is reflected. Due to the inclination of the diffuser plate 3, the disturbance light LS is guided in the figure through the opening 51 of the housing 5 of the head-up display to the outside, where it no longer reaches the eye 42 of the observer anyway and is thus not confusing here.

Fig. 5 shows a part of an exemplary microlens array 310 composed of microlenses 311 or a microlens assembly 330 composed of microlenses 331. The microlens array 310 and the microlens assembly 330 may in principle be constructed similarly, the size of the microlenses 331, 311, their curvature and other optical properties differing from one another according to their function. The microlenses 331, 311 each cover a rectangular area and merge seamlessly into one another. In the illustrated alternative portion of the microlens array 310 or microlens assembly 330, there is an opaque region 319 between the microlenses 331, 311. These regions serve to block light which may be refracted in an undefined manner due to manufacturing inaccuracies of the surface, in the boundary regions of the individual microlenses 331, 311 with one another, and thus avoid confusion which may occur at the viewer.

Fig. 6 shows another microlens array 310 or another microlens assembly 330. In a microlens array or microlens assembly, the microlenses 331, 311 are arranged in a hexagonal closest packing. There is a region 319 between the microlenses 331, 311. Advantageously, this region is embodied to be opaque. Where (otherwise) the incident light can only be refracted correctly through the surface geometry that requires undue effort to be produced onto the opening 51 associated with the adjacent microlens 311, or the light from the opening 51 can only be refracted correctly through the surface geometry that requires undue effort to be produced by one of the respective microlenses 331. Thus, the region 319 is implemented to be opaque and blocks light incident thereon.

Fig. 9 shows a partial enlargement of the region 9 of fig. 2. It can be seen that disturbance light LS1 incident from the outside, which is incident through the opening 321 of the light-shielding mask 32, is reflected on the boundary layer of one of the focusing elements 31, and is incident on the light-shielding mask 32 from immediately below. Thereby avoiding reflections of disturbing light. This advantage is also achieved if the shadow mask 32 is made reflective on its upper side and absorptive on its lower side.

Fig. 10 shows a part of the head-up display corresponding to the lower right part of fig. 1, in which, instead of the display element 1 and the projection system 2, a phase modulator 12 is arranged as an intermediate image generation unit between the light source 11 and the diffuser plate 3. The light path after the turning mirror 44 corresponds to the light path shown in fig. 1 and is therefore not shown again here. Here, the phase modulator 12 is shown as a transmissive device, however, a phase adjuster is also often used as a reflective device. The phase modulator usually also has one or more lenses and, if necessary, further optical elements not shown in this simplified figure.

Fig. 11 shows an example of focusing

elements

31, 315, 316, 317 irregularly arranged on the surface of the diffusion plate 3. In this embodiment, the diffuser plate 3 is a diffuser that can be produced by interference lithography. The focusing

elements

31, 315, 316, 317 also have an irregular shape. Common to the focusing elements is the structural size. Thus, there are no significantly larger or significantly smaller structures. There is a focusing element 315 having a substantially circular shape. The element has similar optical properties as the microlens described above, for example focusing on or close to a point. There is a focusing element 316 having an elongated shape. These elements have an elongated focal point, i.e. a focal line. There is also a focusing element 317 having an irregular shape. This results in an irregular focal spot geometry. The masks produced by means of irradiation according to the method according to the invention accordingly have irregularly distributed irregularly shaped openings which are optimally matched to the irregularly arranged diffuser plate 3 with the shaped focusing

elements

31, 315, 316, 317. This variant has very good suppression of moire patterns.

Fig. 7 shows a manufacturing method according to the invention. In step S1, the assembly 310 of focusing elements 31 is set onto a carrier 3', which carrier 3' already has the diffusing properties of the diffuser plate 3, if necessary. This is indicated by means of an arrow. In step S2, a shadow mask 320 is applied to the opposite side of the carrier 3'. In step S3, a radiation beam SB having defined geometric properties, having a wavelength, intensity and duration suitable for producing the openings 321 in the mask, is irradiated onto the side of the carrier 3' provided with the focusing element 31. Such openings 321 are shown in the previous figures. In step S4, the carrier 3' is combined with the projection system 2 and the display element 1. The projection system 2 is able to generate a radiation beam SB of the defined geometric properties, which, however, differs substantially in wavelength, intensity and/or duration from the radiation beam used for producing the opening. This type of combination is shown, for example, in fig. 1 and 4.

In order to produce the extended diffuser plate 3, it is provided that in step S31, an adhesive 333 is applied to the second side of the diffuser plate 3 on which the shadow mask 32 is provided. In the next step S32, the microlens assembly 330 is applied to the adhesive 333 and then aligned with respect to the focusing element 31 in step S33. After the calibration is completed, the adhesive 333 is cured in step S34. For this purpose, for example, an adhesive 333 curable by means of UV radiation is used. Preferably with UV light from the side facing away from the focusing element 31. Fig. 8 shows a corresponding flowchart in which optional steps S31 to S34 are shown.

In the manufacturing method it is recommended that the illumination is passed through the lens array from the direction of the projection system 2. Subsequently, openings are created in mask 32 in an optimally oriented manner by laser ablation or other interaction of light with the unstructured mask, i.e., light shield layer 320. This is achieved, for example, by a better solubility at the irradiated sites.

In a projection-based windscreen head-up display, in which the driver sees a virtual image VB in the region where he looks out through the windscreen 41, there is a way that the sunlight LS can impinge on a diffuser plate 3, which lies on an intermediate image plane, and onto which the image is projected for the next imaging level to form the virtual image VB. Furthermore, the sunlight LS is more or less partially focused by the imaging stage. In the intermediate image plane there is a diffuser plate 3 or other type of diffuser plate that makes the image visible through a so-called human eye window. By this function, the diffuser plate 3 is often also referred to as Exit Pupil expander (Exit-Pupil-expander). The diffuser plate 3 also reflects a part of the sunlight LS back, whereby the image contrast can be reduced, to be precise whereby this light in the form of undesired and/or disturbing reflections or highlights can be seen to the driver. The invention significantly reduces the reflection of the diffuser plate 3, to be precise turns it in a direction in which it can no longer be seen from the human eye window.

The spatial region in which the observer's eyes 42 must be located in order for the observer to see the virtual image VB completely, i.e. without missing, is referred to as the human eye window. The virtual image VB can only be partially or even not be seen if the observer's eyes 42 are located outside the eye windows. Therefore, if the disturbing light is directed into a spatial region outside the window of the human eye, the stray light LS does not cause at least confusion of the virtual image VB generated by the head-up display. By means of the invention, disturbing reflections are also avoided as far as possible in large, extended human-eye windows. An extended human eye window is also understood to be a region in which: the driver's eyes can be positioned in the area but cannot or can only partially see the heads-up display from the area.

According to the invention, a diffuser plate 3 is constructed with focusing elements 31, for example a microlens array 310. Here, the entrance of the microlens 311 is directed toward the projection system 2. In a basic embodiment, the shadow mask 32 is located on the side on which sunlight is incident, which is designed to allow light from the projection system 2 to pass through the side but block most of the other light. The incident sunlight LS can only pass through the mask 32 via the openings 321 of the mask, the remaining part being absorbed or, in the case of a reflective mask 32, being scattered/scattered into the light trap. Thus, only the remaining reflected light that diverges at the opening 321 or mask 32 returns from the surface. Sunlight that still passes through and is reflected (possibly totally reflected) by the side of the structure facing the projection system 2 must again pass through the mask 32 to show the disturbing effect. Overall, the tendency of the diffuser plate 3 to reflect back, which acts as a pupil expander for the human eye, is significantly reduced by this solution.

According to the invention, the function of the exit pupil expander here assumed by the diffuser plate 3 is supplemented by a special mask 32 which allows the filtering of interfering light. In other variants, light traps or beam shaping are additionally applied. In addition to the basic embodiments, the following variants are mentioned in particular: using a fully absorptive mask, the mask is designed to be single-sided reflective, single-sided absorptive using a fully reflective mask. Other variants have a combination with the second structured surface 33 for further beam shaping. Preferably, the mask 32 is produced by irradiating through the structure itself, for example in combination with a short pulse laser.

Although not explicitly described herein, one of ordinary skill in the art will be able to alter one or more of the above-described features or use them in other combinations without exceeding the spirit of the invention.

Claims

1. A head-up display with a display element (1), a projection/projection system (2), a diffuser plate (3) and mirror elements (4, 41), characterized in that the diffuser plate (3) has a focusing element (31) on its side facing the projection system (2) and a shadow mask (32) on its side facing away from the projection system (2).

2. Head-up display according to claim 1, wherein the shadow mask (32) is made of a material that absorbs light.

3. Head-up display according to claim 1, wherein the shading mask (32) is made of a reflective material and the diffuser plate (3) is arranged inclined with respect to the optical axis of the virtualisation system (44, 45).

4. Head-up display according to any of the preceding claims, wherein the focusing element (31) is constituted by a micro-lens array (310).

5. Head-up display according to claim 4, wherein the microlenses (312 and 314) of the microlens array (310) are arranged obliquely.

6. Head-up display according to one of the preceding claims, wherein the diffuser plate (3) has a further surface structure (33, 34) above the shadow mask (32).

7. Head-up display according to one of claims 1 to 5, wherein the diffuser plate (3) has a further surface structure (35) below the shadow mask (32).

8. Head-up display according to one of claims 6 to 7, wherein the surface structure (33) is a surface structure implementing a field lens function.

9. Head-up display according to one of the preceding claims, wherein the opening (51) of the mask (32) occupies less than 5% of the area of the mask (32).

10. Head-up display according to one of the preceding claims, wherein, instead of the display element (1) and the projection system (2), an intermediate image generation unit is arranged between the light source (11) and the diffuser plate (3), in which intermediate image generation unit the image is first formed on an intermediate image plane.

11. Head-up display according to claim 10, wherein the intermediate image generation unit is one of a phase modulator (12) and a laser scanning system.

12. Head-up display according to any of the preceding claims, wherein the focusing elements (31, 315, 316, 317) are irregularly arranged on the surface of the diffuser plate (3).

13. Head-up display according to claim 12, wherein the focusing element (31, 315, 316, 317) has an irregular shape.

14. Head-up display according to claim 12 or 13, wherein the focusing elements (31, 315, 316, 317) have a common structural dimension.

15. The heads up display according to any one of claims 12-14, wherein the focusing element (31, 315, 316, 317) has at least one of a circular shape, an elongated shape, and an irregular shape.

16. An optical unit for a head-up display according to any of the preceding claims.

17. A method for manufacturing a head-up display, the method having the steps of:

-manufacturing (S1) a focusing element (31) on a first side of the diffuser plate (3);

-applying (S2) a cover layer (320) on a second side of the diffuser plate (3) opposite to said first side;

-irradiating (S3) the first side with a radiation beam (SB) having defined geometrical properties, the radiation beam having a wavelength, intensity and duration suitable for making an opening (321) in the cladding/coating (320);

-combining (S4) the diffuser plate (3) with a projection system (2) capable of generating a bundle of rays having the defined geometrical properties and with a display element (1).

18. The method of claim 17, further having the steps of:

-applying (S31) an adhesive (333) on a second side of the diffuser plate (3);

-applying (S32) a micro-lens assembly (330) on the second side provided with adhesive (333);

-calibrating (S33) the micro-lens assembly (330) with respect to the focusing element (31);

-curing (S34) the adhesive (333).